re: If you want to own an AR-15, you should build it(Posted by Skywalker on 10/22/12 at 1:07 pm to Coon)

Reference from AR15.com This is undoubtedly one of the questions that is asked the most. The answer depends on many things, but here are some rough guidelines for those that don't care about the details: 1-in-14" - 55gr or less 1-in-12" - 35gr up to 55-60gr 1-in-9" - 45gr-75gr, possibly up to 77 if you're lucky 1-in-8", 1-in-7" - 45gr - 80+gr

re: If you want to own an AR-15, you should build it(Posted by Skywalker on 10/22/12 at 1:15 pm to Skywalker)

5.56 NATO vs 223 RemThere always seems to be a lot of confusion over the difference between a .223 and a 5.56 chamber. Is it safe to shoot this? Is it safe to do that? More confusion is added when some manufacturers advertise rifles with .223/5.56 chambers.

The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a .224" diameter, jacketed bullet, with weights ranging from 40 up to 90 grains, though the most common loadings by far are 55 grains.

The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are made from thicker brass than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56mm NATO, is around 78,000 psi tested in .223 Rem test barrels (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56mm round fired is a proof load, very dangerous). The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as the "SAAMI chamber", is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber[2] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the excessive leade. [3] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[4] Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.

re: If you want to own an AR-15, you should build it(Posted by Skywalker on 10/22/12 at 1:17 pm to Skywalker)

Mil-Spec vs CommercialWhat is the difference between the Mil-Spec and the Commercial Receiver Extensions ('buffer tube')? Who uses what? The commercial tubes are slightly larger in diameter where the stock slides, but slightly smaller in diameter when it screws into the receiver. Either can be installed on standard lowers, with the Mil-Spec one actually having the stronger interface (more surface area of the threads engage the receiver).

re: If you want to own an AR-15, you should build it(Posted by bapple on 12/9/12 at 2:41 pm to Purple Spoon)

quote:Can you get hunting calibers in the type of AR platforms? I know you can buy them but can you get the parts for a build?

You could build a 300BLK or a 6.8 SPC. The 6.8 is gonna be more accurate and longer range since it flies faster, but then again I can't completely discount 300BLK because it has some potential. The 300 will be easier to find also.

re: If you want to own an AR-15, you should build it(Posted by Dodd on 12/16/12 at 7:37 pm to thetempleowl)

I'm really trying to fact find on my own, but my ADD may be kicking in. I apologize in advance if my questions are frowned upon by the AR knowlegable folk.

What are the fundamental differences between the various AR Calibers? I'm sure in time, it becomes common knowledge as your basic hunting rifles.

It appears there is the basic plinking caliber in 223 and 556. Is that correct? What if I want to also use it for game hunting (hog, deer). Should I look at the 6.8 or 300 or 308? What are the differences in all mentioned?